JP3001174B2 - Composition for fluorine rubber crosslinking agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for a crosslinking agent used for crosslinking a fluororubber.

[0002]

2. Description of the Related Art Fluororubber is an elastomer excellent in heat resistance, chemical resistance, mechanical strength, etc., and is therefore used industrially in a wide range of fields, mainly in the automobile and machine industries, but is expensive and is processed. There is a problem that sex is bad. This is because the polymer itself is expensive, time is required for kneading the rolls, and the molding is performed at a relatively high temperature for a long time, and secondary molding at a high temperature and a long time is required to obtain stable physical properties. The need for sulfur also increases processing costs and is therefore expensive compared to other elastomers, which limits its industrial applications.

[0003]

For this reason, various improvements have been attempted for the workability. For example, a method has been proposed in which an additive having a siloxane bond is kneaded to improve the roll workability and the mold releasability (JP-A-3-223).
However, since the addition of the silicone component is not compatible with the fluororubber, there is a danger that the silicone component will bleed from the obtained composition, there is a problem in storage stability, and the obtained molded product However, there is a problem in that the mechanical properties of the P.I. A method of blending with another synthetic rubber or polymer for the purpose of cost reduction is also known (see JP-A-60-101135).
The physical properties of the molded product obtained by this method are inferior to those of the original fluororubber, and very few examples have been industrially put to practical use.

[0004] On the other hand, the polyol cross-linked fluororubber is gradually cross-linked by moisture in the air, and thus adversely affects physical properties during operation. As a countermeasure against this, there has been proposed a method of storing in a state of being shielded from the outside air and treating in the presence of a desiccant, under heating with dry heat and under reduced pressure (see Japanese Patent Application Laid-Open No. 58-111848). In order to improve the above drawback, a method using silylated bisphenol AF as a crosslinking agent has been proposed (see JP-A-6-73258). However, although this improved workability, it was found that there was a problem in kneading workability when a large amount of kneading was performed on a mass production scale of 5 kg or more. For example, when a large amount of kneading work is performed due to the melting point of silylated bisphenol AF being 60 ° C. or less, the fluororubber composition generates heat to 80 ° C. or more due to shearing force. Liquid before it is finished,
The phenomenon of slip between kneading rolls may occur.
This is a phenomenon that cannot be seen at all on the prototype scale, and causes a large increase in cost in mass production. Further, when the kneading time is longer, the heat value increases in a mass-produced scale, and there is a risk of scorching, which is not preferable. Also, the silylated polyol may be hydrolyzed and degraded by moisture in the air in a high-humidity environment. Therefore, care must be taken when storing or transferring this product.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a composition for a fluororubber crosslinking agent and a method for producing a polyol-crosslinked fluororubber which have solved the above problems, and which relates to 100 parts by weight of the fluororubber. A composition for a fluororubber crosslinker comprising 20 to 120 parts by weight of a polyol crosslinker in which at least one OH group in one molecule is silylated. A method for producing a polyol crosslinked fluororubber, comprising kneading and crosslinking the composition for a fluororubber crosslinking agent according to claim 1.
Hereinafter, the present invention will be described in detail. The fluororubber constituting the composition of the present invention is a highly fluorinated elastic copolymer, which includes an elastic copolymer of vinylidene fluoride and hexafluoropropene, vinylidene fluoride and pentafluoropropene, and trifluoroethylene. Elastic copolymers with one or more of ethylene, trifluorochloroethylene, tetrafluoroethylene, vinyl fluoride, perfluoro (methyl vinyl ether), perfluoro (propyl vinyl ether) and the like are exemplified. Among them, a vinylidene fluoride-hexafluoropropene binary elastic copolymer and a vinylidene fluoride-tetrafluoroethylene-hexafluoropropene ternary elastic copolymer are preferable. The crosslinking agent is not particularly limited, such as a polyol crosslinking system, an organic peroxide crosslinking system,
Since the composition for a cross-linking agent of the present invention is used for cross-linking a fluoro-rubber of a polyol cross-linking type, it is preferable to use a polyol cross-linking type.

[0006] The silylated polyol crosslinking agent constituting the fluororubber composition of the present invention is the most important component constituting the composition of the present invention. The polyol crosslinking agent is a polyhydroxy aromatic compound or a fluorinated polyhydroxy aliphatic compound, which includes bisphenol A, bisphenol B, bisphenol AF, 1,3,5-trihydroxybenzene, hydroxyresorcin, 2-t-butyl Hydroquinone, 2-methylresorcinol, 1,5-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 2,2-bis (4-hydroxyphenyl) butane,
3,3 ′, 5,5′-tetrachlorobisphenol A,
4,4′-dihydroxydiphenyl, CF ₂ (CF ₂ CH ₂ OH) ₂ ,
HOCH ₂ (CF ₂ ) ₄ OCF (CF ₃ ) CH ₂ OH, CF ₂ (CFHCF ₂ CH ₂ OH) ₂ , (CF ₂ CH
₂ OH) (CF ₂ ) ₃ (CF ₂ CH ₂ OH) and the like. Among them, bisphenol A, bisphenol B, bisphenol AF, 2-t-butylhydroquinone and the like are preferable.
The silylated polyol crosslinking agent is a product in which at least one of the OH groups in the molecule of the polyol crosslinking agent is silylated.
Most preferred are those in which the group is silylated.

As a silylating agent for the polyol crosslinking agent used in the present invention, a compound represented by the following general formula (Chemical Formula 4) (wherein R ⁷ , R ⁸ ,
R ⁹ represents a monovalent organic group which does not react with an OH group or a monovalent organic group containing silicon).

Embedded image These are specifically unsubstituted or substituted monovalent hydrocarbon groups having 1 to 10 carbon atoms (for example, methyl, ethyl, propyl, i-
An alkyl group such as butyl and t-butyl, an aryl group such as phenyl, an alkenyl group such as vinyl, and a group in which part or all of the hydrogen atoms of each of the above groups is substituted with a halogen atom such as a trifluoropropyl group. , And -OSi (CH ₃ ) ₃ , -OSi
And triorganosiloxy groups represented by (CH ₃ ) ₂ C ₆ H ₅ , —OSi (CH ₃ ) ₂ CH = CH _{2 and the} like. Of these, R
Preferred as ⁷ , R ⁸ and R ⁹ are a methyl group, an ethyl group, a phenyl group, a trifluoropropyl group and the like.

On the other hand, X in the above general formula (Formula 4) is a functional group which reacts with an OH group, and includes a hydrogen atom, a chlorine atom, a hydroxyl group,
Amino group, -NHR group (R is a monovalent organic group or a monovalent organic group containing silicon, and includes the same groups as those described above for R ⁷ , R ⁸ , and R ⁹ ) Can be exemplified. In addition, among the above silylating agents, the following formula

Embedded image The hexamethyldisilazane represented by the formula (1) easily reacts with the polyhydroxy compound at room temperature and can be silylated.

The silylated polyol crosslinking agent may be blended in an amount of 20 to 120 parts by weight per 100 parts by weight of the fluororubber. If the amount is less than 20 parts by weight, the amount of the crosslinking agent is insufficient. The kneading of the fluoro rubber becomes difficult. Examples of silylated polyol crosslinking agents represented by the following formulas (6) to (9) are shown.

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[0010] The composition of the present invention preferably contains a catalyst for accelerating crosslinking.

Embedded image (Where R ¹ , R ² , R ³ and R ⁴ are monovalent hydrocarbon groups, Z
Represents a phosphorus atom or a nitrogen atom, and Y represents a halogen atom.
Or represented by the following general formula

Embedded image Wherein R ⁵ and R ⁶ are monovalent hydrocarbon groups, and Y is a halogen atom. Examples of the onium salts are benzyltriphenylphosphonium chloride, bromide, and iminium salts. Preferred are bisbenzylphenylphosphine iminium chloride and the like.

The amount of the catalyst to be added to the composition should be determined in relation to the amount of the crosslinking agent, and is preferably 10 to 100 parts by weight based on 100 parts by weight of the crosslinking agent. If the amount is less than 10 parts by weight, the crosslinking reaction may be insufficient. If the amount is more than 100 parts by weight, the effect remains unchanged and is uneconomical.

The composition for a fluororubber crosslinking agent of the present invention can be obtained by mixing and kneading a predetermined amount of the fluororubber and the silylated polyol crosslinking agent. Since it is desirable to completely disperse these components in this kneading, if a work suitable for the compounding conditions is performed using a conventionally used two-roll rubber roll, a pressure kneader, a kneader, a Banbury mixer, or the like. According to this, the composition can be obtained with good workability without using a special device. When the amount of kneading is large and a large amount of heat may be generated, it is preferable to remove heat by circulating water in the apparatus. . Regarding the use of other fillers, conductive materials, heat dissipating agents, coloring agents, etc., there is no problem in using them in amounts within the range suitable for the intended purpose. The composition for a fluororubber crosslinking agent of the present invention can be easily kneaded as a crosslinking agent for a polyol crosslinking fluororubber. Examples of the polyol cross-linked fluororubber include those similar to the above-mentioned elastic copolymers, and those containing vinylidene fluoride are particularly preferable. In this case, a crosslinking agent in which at least one of the OH groups contained in the fluororubber crosslinking agent is silylated,
0.05 to 100 parts by weight of polyol crosslinked fluororubber
It is preferable to mix and knead 5 parts by weight, especially 1 to 3 parts by weight. Then, crosslinking may be performed under known crosslinking conditions that are usually performed.

[0013]

Next, the present invention will be described with reference to examples, but the present invention is not limited to these examples. Prior to the description of the examples and the like, the source of the materials and equipment used and synthesis examples of the silylated polyol crosslinking agent will be described. (Materials and Equipment Used in Examples and Comparative Examples) Fluororubber (polyol cross-linked vinylidene fluoride-hexafluoropropene binary copolymer) FC2145
(Trade name, manufactured by Sumitomo 3M) Calcium hydroxide, Caldic 2000 (trade name, manufactured by Omi Chemical Industry Co., Ltd.) Magnesium oxide, Kyomag # 150 (trade name, manufactured by Kyowa Chemical Co., Ltd.) Carbon black, MT carbon black (Harber product name) Catalyst (benzyltriphenylphosphonium chloride)
・ (Made by Kanto Chemical Co., Ltd.) Melting point measuring device ・ BY-1

(Synthesis of Silylated Polyol Crosslinking Agent) In a fume hood, in a separable flask containing 1,680 g (5 mol) of bisphenol AF and 2,500 g of toluene as a solvent, hexamethyl was added at room temperature (25 ° C.). When 965 g (6 mol) of disilazane was added and the mixture was stirred and reacted for 3 hours, when the reaction started, slight heat generation and generation of ammonia gas were confirmed. After completion of the reaction, toluene and unreacted hexamethyldisilazane were removed under reduced pressure to obtain 2,230 g of white crystals (93% yield). When this white crystal was analyzed by IR and NMR, it was confirmed from the FT-IR chart that both ends of the molecular chain were silylated.

Embedded image It was confirmed that the product was obtained by the following method. This white crystal was 52 ° C. when measured with a melting point measuring apparatus. (Preparation of Sample for Measurement of Physical Properties) A sheet having a thickness of 2 mm was prepared under press molding conditions of 170 ° C. for 10 minutes; and post cure conditions at 230 ° C. for 24 hours.

(Example 1) Crosslinking agent 1 was prepared by adding 500 g of silylated bisphenol AF to 1 kg of fluororubber and kneading with an 8-inch double roll. Using this as a cross-linking agent master batch, a fluororubber was kneaded with the following composition. For kneading, use 18 inch double rolls,
The workability and physical properties at a scale of 10 kg were confirmed, and the results are shown in Table 1. Fluoro rubber 100 parts by weight Calcium hydroxide 6 parts by weight Magnesium oxide 3 parts by weight MT carbon black 10 parts by weight Catalyst 0.5 parts by weight Crosslinking agent 16 parts by weight

Example 2 A crosslinker 2 was prepared by adding 500 g of silylated bisphenol AF to 500 g of fluororubber and kneading the mixture. Using this as a cross-linking agent master batch, a fluororubber was kneaded with the following composition. The kneading was performed using a roll of 8 inches and the workability and physical properties were confirmed on a scale of 5 kg of fluororubber, and the results are shown in Table 1. Fluororubber 100 parts by weight Calcium hydroxide 6 parts by weight Magnesium oxide 3 parts by weight MT carbon black 10 parts by weight Catalyst 0.5 parts by weight Crosslinking agent 24 4 parts by weight

Example 3 A crosslinking agent 3 was prepared by adding 250 g of silylated bisphenol AF and 70 g of a catalyst to 1 kg of fluororubber and kneading the mixture with a pressure kneader. Using this as a cross-linking agent master batch, a fluororubber was kneaded with the following composition. The kneading was performed using a roll of 8 inches and the workability and physical properties were confirmed on a scale of 5 kg of fluororubber, and the results are shown in Table 1. Fluoro rubber 100 parts by weight Calcium hydroxide 6 parts by weight Magnesium oxide 3 parts by weight MT carbon black 10 parts by weight Crosslinking agent 3 10 parts by weight

Comparative Example 1 The content of the crosslinking agent 1 used in Example 1 was changed to that of silylated bisphenol AF alone.
When the kneading was carried out with the same composition as that of (i.e., only the amount of the crosslinking agent was different), the physical properties of the composition were the same, but the kneading workability was inferior and required three times as long as in the examples. Workability and physical properties were confirmed, and the results are shown in Table 1. Fluororubber 100 parts by weight Calcium hydroxide 6 parts by weight Magnesium oxide 3 parts by weight MT carbon black 10 parts by weight Catalyst 0.5 part by weight Crosslinking agent 2 parts by weight (Comparative Example 2) Polymer base having the same composition as Comparative Example 1 The kneading time when the scale was 1 kg was 30 minutes, which was not much different from Example 1. Workability and physical properties were confirmed, and the results are shown in Table 1.
It was shown to. (Comparative Example 3) When 200 parts by weight of silylated bisphenol AF was added to 100 parts by weight of fluororubber and kneaded, the kneading workability was poor, and 10 parts of silylated bisphenol AF were added.
When added in an amount of 0 parts by weight or more, it did not wind around the roll, making it impossible to continue the work. Workability and physical properties were confirmed, and the results are shown in Table 1.
It was shown to.

[0019]

[Table 1]

[0020]

By using the composition of the present invention as a cross-linking agent master batch, the kneading time on a mass production scale of fluororubber can be greatly reduced, and the cross-linking time and the cross-linking temperature can be reduced. It becomes possible. In addition, handling by physical distribution as a cross-linking agent becomes easy.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-73258 (JP, A) JP-A-6-128440 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 27/12-27/20

Claims (4)

(57) [Claims] 1. 100 parts by weight of fluororubber and O in one molecule
A composition for a fluororubber crosslinker, comprising 20 to 120 parts by weight of a polyol crosslinker having at least one H group silylated. 2. The composition for a fluororubber crosslinking agent according to claim 1, wherein the silylated polyol crosslinking agent is represented by the following chemical formula (1). Embedded image 3. A catalyst of the general formula (2) wherein R
¹ , R ² , R ³ , and R ⁴ are monovalent hydrocarbon groups having 1 to 20 carbon atoms, Z is a phosphorus or nitrogen atom, Y is a halogen atom) or a compound represented by the general formula (3) (where R ⁵ , R ⁶ 2. The fluororubber according to claim 1, which contains an onium salt or an iminium salt represented by a monovalent hydrocarbon group having 1 to 20 carbon atoms and Y is a halogen atom) in an amount of 10 to 100 parts by weight based on 100 parts by weight of the polyol crosslinking agent. A composition for a crosslinking agent. Embedded image Embedded image 4. A process for producing a polyol cross-linked fluororubber, comprising kneading and cross-linking the composition for a fluororubber crosslinker according to claim 1 into the polyol cross-linked fluororubber composition.